In the manufacturing or processing of a number of vegetable base beverages, notably beer, ale, wine and fruit and vegetable juices the beverage is filtered one or more times to remove certain deleterious materials. For example, see U.S. Pat. No. 4,134,857 entitled "Use of Tannic or Gallic Acid to Produce Low Beverage Soluble Iron Content Filter Aid". It is desirable to control the presence of beverage soluble iron since beverage soluble iron can be deleterious to the taste and long term stability (shelf-life) of the beverage.
The problem of beverage soluble iron migration into the pack may occur in any pack containing an acid system. The problem may be especially critical in cans and bottles containing beer. As little as 60 parts per billion iron may effect the taste of beer. It has also been recognized, that though the taste of beer is not affected, the presence of beverage soluble iron may cause the beer to be cloudy and thus unacceptable from the consumer's point of view.
The beverages mentioned above may be packaged in either cans or bottles. In either case the beverage pack may come in contact with the container or the sealing materials used in manufacturing the container where beverage soluble iron may be present. In the case of bottles, the metal or sealing material with which the beverage pack comes in contact with is the closure which may be either a crown closure or a roll-on type closure. In the closure or cap there is provided an annular sealing gasket on the interior surface to provide a seal between closure and the bottle.
Over the years can manufacturers have been providing metal containers for packaging beer. These containers may be either an aluminum can, a coated steel can, or a combination thereof. Recent technology development has provided easy open ends and ecology ends for cans having pressurized contents. For example see U.S. Pat. Nos. 4,124,139; 4,134,517 and particularly U.S. Pat. No. 3,931,909. U.S. Pat. No. 3,931,909 teaches the use of sealants based on polyvinyl chloride to seal the partially severed opening.
Easy open beer ends ecology ends are made from organic enamel coated electrolytic chromium coated steel and are made by partially cutting openings through the steel and resealing the partially cut openings with a plastisol sealing material. For the most part the organic enamel coating provide an excellent barrier to corrosion. The sealant is designed to provide a mechanical seal in the partially cut opening or scored areas and provide a gas and liquid seal and still be easily torn so that the container may be opened.
The pack environment is such that the acid beverage comes in contact with the container walls and the sealing materials therein. Any beverage soluble iron on the container walls or in the sealing materials may be leached into the pack under certain conditions. Certainly the most likely sources of iron contamination would be the scored steel ends in the case of acid pack beverages packaged in cans and the steel crown caps in the case of acid pack beverages packaged in glass or plastic containers.